Arteries (pink) grow alongside nerves (green) in the skin.
Arteries branch and extend in an intricate pattern worthy of a Michelangelo painting. But it's more like a tracing than an original work of art, according to new results from Yoh-suke Mukouyama, David Anderson (California Institute of Technology, Pasadena, CA), and colleagues. They find that the original artwork is the nerve network.Anderson's group observed that peripheral nerves in the limbs of mice are aligned along arterial vessels. More than a coincidental association, the presence of these nerves actually specified arterial differentiation. When nerves were misrouted, arteries became similarly patterned along the altered nerve route. Veins, on the other hand, were not affected. “Nerves in limbs go where the action is, to muscle and skin,” says Anderson. “There's a lot of metabolic activity there that needs oxygen. So it makes sense that arteries would take the same path taken by nerves.”
Nerve cells probably direct arterial organization and formation by secreting the endothelial mitogen VEGF. In vitro, VEGF induced arterial differentiation of endothelial cells, and mutant mice that lack Schwann cells and whose arteries and nerves had lost their association also had reduced expression of VEGF in their nerve cells. Anderson plans to confirm VEGF involvement in this process by examining mice that completely lack VEGF expression in peripheral nerves. ▪